Video tape control time code reading

Abstract

A video magnetic tape control time code reading method and apparatus employs a control time code comprising binary coded times and frame numbers which together form addresses of individual frames of a video signal recorded on a video magnetic tape which can be read, independently of the direction and speed of transport of the video tape, to ascertain whether the control time code corresponds to a recorded video signal having a frame frequency of 30 or 25 frames per second. Use is made of the fact that certain frame numbers occur in a 30 frame per second control time code which do not occur in a 25 frame per second control time code.

I claim: 
     
       1. A method for distinguishing between first and second control time codes recorded on a recording tape, said first and second control time codes including frame numbers sequentially repeating and having equal minimum values and said first control time code having a first maximum value which exceeds a second maximum value of said second control time code, said recording tape being transportable in a forward tape transport direction and in a reverse tape transport direction, said frame numbers sequentially increasing from said minimum to said maximum value during forward tape transport and sequentially decreasing from said maximum to said minimum value during reverse tape transport, comprising the steps of: detecting whether tape transport is in said forward or reverse tape transport direction;   comparing a first frame number in a first frame with a next-occurring frame number;   during forward tape transport, producing an output signal indicative of said first control time code in response to said first frame number being said second maximum value and said next-occurring frame number being other than said minimum values; and   during reverse tape transport, producing an output signal indicative of said first control time code in response to said first frame number being said minimum values and said next-occurring frame number being other than said second maximum value.   
     
     
       2. A method for distinguishing between first and second different control time codes having at least frame codes which identify repeating sequences of contiguous frame numbers therein reproduced from a video magnetic tape containing video signals recorded thereon, comprising the steps of: sensing the presence and absence of predetermined frame numbers in the reproduced control time code; and   detecting in dependence on the presence and absence of said predetermined frame numbers, whether said reproduced control time code is said first or said second control time code.   
     
     
       3. A method according to claim 2 wherein said first control time code corresponds to a video signal having 30 frames per second, said second control time code corresponds to a video signal having 25 frames per second, and said sensing step comprises sensing the frame numbers corresponding respectively to highest and lowest frame numbers in said second control time code. 
     
     
       4. A method according to claim 3 wherein said sensing step further comprises sensing the frame codes identifying respectively a frame number one higher than said highest frame number in said second control time code and a frame number corresponding to the highest frame number in said first control time code. 
     
     
       5. A method for distinguishing between at least first and second control time codes reproduced from a video tape which contains frames of video recorded thereon, said first control time code including at least first repeating sequences of frame codes identifying individual frames of said video, said first repeating sequences repetitively beginning with a first number and ending with a second number, said second control time code including at least second repeating sequences of frame codes identifying individual frames of said video, said second repeating sequences repetitively beginning with said first number and ending with a third number which is greater than said second number, comprising the steps of: sensing one of said first, second and third numbers; and   sensing whether a next-occurring frame code after said sensing of said one of said first, second and third numbers includes a next frame number in one of said repeating sequences and producing in dependence thereon an output signal indicative of one of said first and second control time codes.   
     
     
       6. A method according to claim 5, further comprising: selectively transporting said video tape in first and second directions;   sensing the direction of tape transport; and   said step of sensing one of said first, second and third numbers includes selectively sensing one of said first, second and third numbers upon transport of said video tape in said first and second directions, respectively.   
     
     
       7. A method according to claim 6, further comprising: selectively sensing said third number and a fourth number which is one greater than said second number; and   sensing whether said next-occurring frame code after sensing said first number includes said third number or whether a next-occurring frame code after sensing said second number is said fourth number and producing, in dependence thereon, an output signal indicative of said second control time code.   
     
     
       8. A method according to claim 5, further comprising sensing whether said next-occurring frame code after sensing of said one of said first and second numbers includes either said third number or a fourth number which is one greater than said second number and producing in dependence thereon a second output signal indicative of said second control time code. 
     
     
       9. A video tape control time code reading apparatus for distinguishing one of at least first and second different control time codes having frame numbers corresponding respectively to frames of video signals having first and second different frame frequencies recorded on said video tape, the apparatus comprising: means for receiving said control time code;   means for sensing the presence and absence of predetermined frame numbers within said control time code; and   means operative in dependence on the presence and absence of said predetermined frame numbers, for distinguishing between said control time code being said first and said second time code.   
     
     
       10. A video tape control time code reading apparatus according to claim 9 wherein said first frame frequency is 30 frames per second, said second frame frequency is 25 frames per second, and said means for sensing includes means for sensing said frame numbers corresponding respectively to a highest and a lowest frame number in said second control time code. 
     
     
       11. A video tape control time code reading apparatus according to claim 10, wherein said means for sensing further includes means for sensing a frame number one higher than said highest frame number in said second control time code and a frame number corresponding to the highest frame number in said first control time code. 
     
     
       12. A video tape control time code reading apparatus according to claim 9, wherein said first frame frequency is 30 frames per second and said second frame frequency is 25 frames per second, said video tape having at least a forward direction of tape transport, and said apparatus comprises means for generating a first signal indicating at least said forward direction of tape transport, means for generating a first pulse in response to the highest frame number in said second control time code, means for delaying said first pulse for one frame period, means for generating a second pulse in response to a frame number one higher than said highest frame number in said second control time code, and means for detecting simultaneous existence of said delayed first pulse and said second pulse while said first signal indicates said forward direction of tape transport and thereupon supplying an output signal indicating that said frame frequency is 30 frames per second, and for detecting simultaneous existence of said delayed first pulse and absence of said second pulse while said first signal indicates said forward direction of tape transport and for thereupon supplying an output signal indicating that said frame frequency is 25 frames per second. 
     
     
       13. A video control time code reading apparatus according to claim 12 wherein said video tape also has a reverse direction of tape transport, further comprising said means for generating a first signal being further operative to indicate said reverse direction of tape transport, means for generating a third pulse in response to a lowest frame number in said first and second control time codes, means for delaying said third pulse for one frame period, means for generating a fourth pulse in response to the highest frame number in said first control time code, and means for detecting simultaneous existence of said delayed third pulse and said forth pulse while said first signal indicates said reverse direction of tape transport and for thereupon supplying an output signal indicating a frame frequency of 30 frames per second, and for detecting existence of said delayed third pulse and absence of said fourth pulse while said first signal indicates said reverse direction of tape transport and for thereupon supplying an output signal indicating a frame frequency of 25 frames per second. 
     
     
       14. A video tape control time code reading apparatus according to claim 9 wherein said means for receiving includes means for storing a portion of said one control time code corresponding to one frame of said video signal, and means for extracting from said portion at least said frame number. 
     
     
       15. A video tape control time code reading apparatus according to claim 14 wherein said video tape has first and second tape transport directions and said means for receiving includes means for determining said transport direction in dependence on said one control time code and for supplying a direction signal indicating one of said first and second tape transport directions.